The present invention relates to heavy-duty driveline friction clutches of the type used for large vehicles such as trucks, tractor-trailers and the like, and more particularly, to a clutch brake assembly for use in a driveline friction clutch.
The use and function of a clutch brake is well known in the art, as discussed, for example by Kronstadt (U.S. Pat. No. 5,713,443), Allen, Jr. et al. (U.S. Pat. No. 5,957,256) and Weigand et al. (U.S. Pat. No. 5,415,256) the disclosures of which are hereby incorporated by reference in their entirety. A clutch brake is a device used to rapidly slow the rotational speed of a transmission input shaft when a driveline master clutch is disengaged to facilitate the shifting of gears in the transmission. Without a clutch brake, the time required to shift a transmission would be significantly increased, thereby complicating the operation of the transmission in several driving modes.
Typically, the clutch brake is a disc-shaped device, a portion of which is splined to the input shaft of the transmission and is activated by a master clutch release mechanism when the master clutch is disengaged. Upon disengagement of the master clutch, friction elements of the clutch brake are pressed between a transmission housing and the release mechanism creating a frictional drag or braking force that slows the spinning transmission input shaft to facilitate gear shifting.
Normally, a release bearing, which is the operating portion of the release mechanism, moves between engaged (near the clutch) and disengaged (nearer the transmission) positions causing the master clutch to selectively connect and disconnect the transmission input shaft from the engine. When the release bearing is moved within a normal shifting range, the clutch brake is not engaged. However, when it is desired to rapidly slow the rotation of the transmission input shaft to facilitate a gear shift, the release mechanism is moved beyond the normal shift range so as to trap and clamp the clutch brake between the release bearing and the transmission housing. When so moved, the rotation of the clutch brake disc and consequently the transmission input shaft is slowed or stopped.
In normal use, the frictional elements of the clutch brake eventually wear out and must be replaced. The process of replacing the clutch brake requires lowering and disconnection of the transmission to remove and replace the clutch brake friction elements. The prior art teaches two-piece discs that allow removal and installation of the clutch brake without partially disassembling the clutch or transmission. However, such clutch brakes have multi-piece structures that still render them laborious to remove and re-install given the limited space present between modern clutches and transmissions.
The present invention provides an improved structure for a shaft brake that can be easily installed and removed from a shaft. In a preferred embodiment, the brake includes a friction disc assembly comprising two opposing xe2x80x9cUxe2x80x9d shaped friction discs separated by at least one resilient biasing member. A brake disc is sandwiched between the friction discs of the friction disc assembly and is splined to rotate with a shaft, such as a transmission input shaft. A side of each friction disk that faces the brake disc is covered with a friction material. In normal operations, the friction discs are spaced apart from the brake disc by the biasing member. When it is desired to slow the rotation of the shaft, a release member contacts and compresses the friction disc assembly against a housing causing the friction material on each of the friction discs to contact the brake disc.
In a preferred embodiment, the friction discs include an open section for disposing the friction disk assembly about the shaft. A slot in communication with the open section facilitates installation and removal of the friction disk assembly around the shaft. The friction disk assembly is preferably removably secured to the housing by at least one fastener.
The present invention is particularly suited for use as a clutch brake for slowing rotation of an input shaft disposed between a clutch and a transmission of a vehicle. Among other advantages, the clutch brake of the present invention includes a friction disk assembly that may be easily installed and removed without disassembling the clutch or the transmission. The friction disk assembly advantageously provides a friction disk on each side of a brake disc without requiring that an individual disk be secured to both a master clutch release member and a transmission housing.
Various additional aspects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.